/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.core.convert.support;

import org.springframework.core.convert.ConversionService;
import org.springframework.core.convert.TypeDescriptor;
import org.springframework.core.convert.converter.ConditionalGenericConverter;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.StringUtils;

import java.lang.reflect.Array;
import java.util.Collections;
import java.util.Set;

/**
 * Converts a comma-delimited String to an Array.
 * Only matches if String.class can be converted to the target array element type.
 *
 * @author Keith Donald
 * @author Juergen Hoeller
 * @since 3.0
 */
final class StringToArrayConverter implements ConditionalGenericConverter
{

    private final ConversionService conversionService;


    public StringToArrayConverter(ConversionService conversionService)
    {
        this.conversionService = conversionService;
    }


    @Override
    public Set<ConvertiblePair> getConvertibleTypes()
    {
        return Collections.singleton(new ConvertiblePair(String.class, Object[].class));
    }

    @Override
    public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType)
    {
        return ConversionUtils.canConvertElements(sourceType, targetType.getElementTypeDescriptor(), this.conversionService);
    }

    @Override
    @Nullable
    public Object convert(@Nullable Object source, TypeDescriptor sourceType, TypeDescriptor targetType)
    {
        if (source == null)
        {
            return null;
        }
        String         string            = (String) source;
        String[]       fields            = StringUtils.commaDelimitedListToStringArray(string);
        TypeDescriptor targetElementType = targetType.getElementTypeDescriptor();
        Assert.state(targetElementType != null, "No target element type");
        Object target = Array.newInstance(targetElementType.getType(), fields.length);
        for (int i = 0; i < fields.length; i++)
        {
            String sourceElement = fields[i];
            Object targetElement = this.conversionService.convert(sourceElement.trim(), sourceType, targetElementType);
            Array.set(target, i, targetElement);
        }
        return target;
    }

}
